Find the number of terms in the given AP.
AP: 7, 10, 13, ..., 43.
tn=a1+(n−1)d
where,
'a1' is the first term,
'd' is the common difference,
'n' is the number of terms,
'tn' is the nth term.
Given, tn = 43, a1=7, a2 = 10
d = a2 - a1 = 10-7 = 3
Substituting these values in the equation, we get,
43=7+(n−1)3
43-7 = (n-1)3
⇒ 36 = (n-1)3
⇒ 12 = n-1
⇒ n =13